Coil bobbin and matching cover



1966 R. w. JOHNSON COIL BOBBIN AND MATCHING COVER Filed Nov. 9, 1962 A I allillii. 4 a Q INVENTOR ROBHPT W JOHNSON United States Patent C) 3,230,490 COIL BOBBIN AND MATCHING COVER Robert Warren Johnson, Chicago, Iil., assignor to Guardian Electric Manufacturing Co., Chicago, 11]., a corporation of Illinois Filed Nov. 9, 1962, Ser. No. 236,519 3 Claims. (Cl. 336-498) This invention relates to a bobbin and cover assembly and, more particularly, to a molded insulating bobbin and cover assembly for use in the manufacture of an electrical coil assembly.

Electrical coil assemblies, such as used for example in transformers, relays, solenoids and inductors, have here tofore been conventionally made by winding a continuous length of insulated magnet wire onto a core piece of a spool or bobbin. The coating on .the wire provided insulation between the adjacent turns of the wire. It was found that the insulation was often damaged during manufacture of the electrical coil assembly and that additional insulation was needed for many applications to prevent short circuiting between turns of the wire and between the leads. Thus, it was found expedient to impregnate the formed coil with varnish and then bake the same. For some uses, the varnishing and baking procedures were repeated at second time. Afterwards, insulating tape was aflixed about the coil to minimize mechanical damage thereto. This electrical coil assembly manufacturing procedure was obviously slow and relatively expensive.

The electrical coil assemblies are comm-only provided with a plurality of conductive terminal lugs on the bobbin, such lugs being secured to the ends of the wire forming the coil. A problem found in such constructions is that the connections of the wire to the lugs cannot inherently be insulated from one another or from other components in the circuit or in the electrical assembly adjacent to the coil without the use of added secondary insulating tapes or the like.

I-Ieretofore, the electrical coil assembly was generally positioned on the support therefor without provision of means to prevent the electrical coil from rotating with respect to the support and for spacing the electrical coil from the support.

A primary object of the present invention is to overcome the deficiencies and disadvantages of prior coil constructions by providing a novel molded bobbin and cover assembly for an electrical coil assembly.

Another object of the present invention is to provide a novel bobbin and cover assembly for an electrical coil assembly wherein the cover frictionally engages the bobbin to define an enclosed insulated chamber therebetween for containing the continuous wire forming the coil.

Yet another object of the present invention is to provide a unique molded bobbin and cover assembly wherein the lead wires for the coils are effectively spaced and insulated from one another.

A further object of this invention is to provide a bobbin and cover assembly for an electrical coil construction which provides superior mechanical protection for the coil and which can be manufactured easily and inexpensively.

A further object of this invention is to provide a bobbin and cover assembly having means for indexing and spacing the bobbin and cover assembly on the support therefor.

Still another object of the present invention is to provide a molded bobbin and cover assembly for an alternating current relay which includes means on the cover thereof for supporting the field piece of the relay.

An important feature of the invention resides in the fact that the bobbin and the cover are each formed from a resinous insulating material and that the two components are adapted to frictionally engage one another to define an enclosed insulated chamber for receiving a continuous length of wire.-

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The specific details of a preferred embodiment of the invention and their mode of functioning will be made most manifest and particularly pointed out in clear, concise and exact terms in conjunction with the accompanying drawing, wherein:

FIGURE 1 is a side view of a relay utilizing the bobbin and cover assembly of the present invention;

FIGURE 2 is an exploded perspective vie-w of the bobbin and cover assembly of the present invention with the wire forming the coil being omitted;

FIGURE 3 is a longitudinal cross-sectional view of the bobbin and cover assembly of this invention;

FIGURE 4 is a fragmentary detail view of the bobbin and cover assembly with a portion of the cover illustrated in cross section;

FIGURE 5 is a fragmentary rear view of the bobbin with parts broken away;

FIGURE 6 is a detail view illustrating the initial connection of a conductive terminal lug to an opening in the base flange of the bobbin;

FIGURE 7 is a detail view illustrating the connection of the conductive terminal lug in the opening in the base flange of the bobbin after an end of wire forming the coil is secured to the lug and lug is seated in the opening, and also illustrating in dotted line the position of the lug after it is bent; and

FIGURE 8 is a fragmentary view illustrating the loop formed in the wire adjacent the conductive terminal lug and the protective lug formed on the base flange of the bobbin for protecting the loop from damage.

Referring now more particularly to the drawing, lifle numerals in the various figures will be taken to designtae like parts.

In FIGURE 1, the invention is illustrated as applied to an alternating current relay 10. It will be apparent to those versed in the art that the principles of the present invention, which are hereinafter more fully described, may be utilized in various types of electrical coil assemblies, as for example, transformers, inductors, relays, and solenoids. The relay It) comprises a field piece 12 upon which is supported a molded coil and cover assembly 14. The molded cover and coil assembly 14 is provided with means 16 for positioning and spacing the molded coil and cover assembly on the field piece or support frame 12. It is to be noted that that the means 16 extends into a recess 18 defined in a portion of the field piece 12.

On the top of the cover there are provided means for receiving the shading piece 20 of the conventional alternating current relay, such shading piece being positoned between the fastening means 21 for affixing the relay on the field piece 12 and the top of the cover of the molded coil and cover assembly.

Referring now to FIGURE 2, there is illustrated an exploded perspective view of the cover 22 and the bobbin or spool 24 comprising the molded spool and cover assembly 14. The Wire forming the coil has been omitted for the sake of clarity and the ends of the conductive lugs are shown in the bent position after the coil has been formed and the leads of the wire forming the coil have been secured to the conductive lugs.

The bobbin or spool 24 comprises a central portion or tubular member 26 to the ends of which are fastened a generally annular flange 28 and a flange 30 defining a base. The member 26 may be cylindrical, as shown, or may take a variety of shapes depending upon the use of the electrical coil assembly. Embedded in one end of the flange 30 are a pair of conductive terminal lugs 32.

Formed in the flange 30 between the conductive terminal lugs 32 is an undercut groove or pocket 34. As is clearly shown in FIGURE 2, the undercut groove tapers outwardly from a point adjacent the cylindrical tube 26 to a point adjacent the periphery of the flange between the two conductive lugs 32.

At a point in the base flange 30 remote from the two conductive terminal lugs, there is provided a notch or recess 36. The recess 36 connects with a groove 38 formed in the periphery of the flange 30. The groove 38 extends along one side of the base flange 30 from a position adjacent the recess 36 to a position adjacent the right terminal lug 32. It is clear that the starting lead of wire connected to the left terminal lug 32 is positively spaced from and insulated from the terminal lead of wire connected to the right terminal lug 32.

Formed on the base flange 30 beneath the conductive terminal lugs 32 is a shelf or lip 39 which projects forwardly and outwardly from the base. The shelf 39 provides an insulating barrier beneath the conductive terminal lugs 32. The shelf may be formed as a lip beneath each terminal lug, but it is preferred that it be a unitary member extending beneath both terminal lugs.

During assembly of the conductive terminal lugs 32 to the base 30, a loop is formed in the terminal lead of the conductive wire defining the coil, such loop being formed adjacent the outer end of the right conductive terminal lug 32. To prevent the loop from being damaged, a projection 40 extends from the top surface of the base flange 30 over the loop of wire and over shelf 39.

Considering now the cover 22, it is seen that the cover comprises an inverted cup-shaped member, which incudes an integral annular, disc-like top 42 having a recess 44 therein of a complementary configuration to that of the shading piece 20 of the relay. The cover 22 also includes a tubular portion 46, which is adapted to surround and enclose the flange 28 and the tubular member 26 and a horizontally extending housing portion 48, which extends forwardly from the tubular portion 46, and encloses the forward portion of base flange 30, such cover and bobbin defining therebetween an enclosed, insulated chamber. Provided in the top of the horizontally extending housing portion 48 are a pair of openings 50 adapted to receive the upwardly extending portions or legs of conductive terminal lugs 32. The housing portion 48 also includes a downwardly extending wall 52 from the forward end of which there extends a protective shelf or lip 54.

Means are provided for frictionally engaging the cover 22 and the bobbin 24. Such means may comprise a bead 56 defined on the interior of the cover 22 adjacent the bottom thereof, such bead cooperating with the bottom of the base flange 30 so as to provide for a snap-on connection of the cover 22 to the bobbin 24.

Referring now to FIGURE 3, it is seen that the means 16 for positioning and spacing the molded bobbin and cover assembly on support means therefor comprises a spacing lug 60 and an indexing lug 62, the latter lug 62 being adapted to engage in recess defined in the support means. Obviously, in certain applications of an electrical coil assembly using the molded bobbin and cover of this invention, the means 16 may be omitted.

It is also to be noted that the conductive terminal lugs 32 have a plurality of arrow-like barbs 64 formed on an end thereof, such barbs or serrations being adapted to engage the interior of the opening 66 defined in the base flange for embedding the conductive terminal lugs 32 in the openings in the base flange 30.

The top flange 28 of the spool 24 engages the underside of the top 42 of the cover 22 and forms a seal therewith. The bead 56 defined on the cover 22 adjacent to the bottom thereof engages the base flange 30 so as to detachably engage the cover to the bobbin and the two assemblies are constructed and arranged to define an enclosed, insulated chamber 68 therebetween, Within which chamber the coil of the conductive wire 72 is adapted to be retained.

The spool or bobbin 24 and the cover 22 are prefer- 4 ably molded from a thermoplastic resin or from other resinous materials such as nylon, polyethylene, or a similar material which has good dielectric properties and is easily molded under heat and pressure.

Referring to FIGURE 4, there is shown a fragmentary view from the front of the cover and bobbin assembly. Formed in the end of the base flange 30 are a pair of openings 66 which are adapted to receive the conductive terminal lugs 32. Provided between the two openings 66 is an undercut groove or pocket 34 which opens to the top of the base flange through a slot 70.

As is apparent from FIGURE 4, the means 16 for positioning and spacing the molded bob-bin and cover assembly on a support are centrally located and depend downwardly from the base flange 30.

FIGURE 5 is a detailed view illustrating the rear of the bobbin. It is seen that the recess or notch 36 in the top surface of flange 30 communicates with the groove 38 in the side of the flange. A wire in the groove will thus be protected against damage and will be insulated on three sides. When the cover is positioned on the bobbin the wire will be fully protected and insulated.

Considering now FIGURES 6, 7 and 8, there is illustrated the manner of engaging a conductive terminal lug 32 in an opening 66 in the base flange 30. Initially, the lug 32 is inserted into the opening 66 until it is approximately adjacent the end of the opening. The lead or end of the wire 72 is then wound about the median portion of the lug 32 and aflixed thereto, as for example, by means of a drop of solder. Assuming now that the starting lead of the continuous length of wire 72 has been secured to the left-hand lug 32, as seen in FIGURE 2, the wire is inserted through the undercut groove 34 and wound about the central portion 26 of the spool in the winding space formed between the flanges 28 and 30 to define a coil. After the proper number of turns have been wound about the central portion 26, the terminal lead or end of the wire is inserted through the recess 36 in the top of the base flange 30 into the groove 38 defined in the periphery of the base flange 30. The terminal lead of the continuous wire is then aflixed to the median portion of the righthand terminal lug 32. After each end of the conductive wire'has been afiixed to the generally planar terminal lug 32, as indicated in FIGURE 6, the terminal lugs 32 are forced into the openings 66 until the ends are approximately seated, this movement of the lugs 32 being a distance of approximately to l of an inch. Pushing the conductive terminal lugs 32 toward the base firmly engages the lug within the base flange 30 and also provides slack or a loop adjacent the terminal lugs. This loop is necessary to compensate for contraction and expansion of the continuous length of wire during operation of the electrical coil assembly.

After the terminal lugs are firmly embedded in the opening 66 in the base flange 30, as indicated in solid line in FIGURE 7, the end of the terminal lug 32 is bent approximately degrees to form a lug generally L- shaped in cross section, as indicated in the dotted line position in FIGURE 7.

Considering now FIGURE 8, there is illustrated a fragmentary top view showing the connection of a terminal lug 32 to the base flange 30. Upon seating the terminal lug in the opening 66, a loop 74 is formed in the conductive wire 72. The projection 40 extending outwardly over the lower shelf 39 cooperates with the shelf to define a mechanical protection for the loop and to prevent damage thereto during subsequent manufacture.

After completion of the bobbin, the cover 22 may be snapped onto the bobbin so as to define therebetween an insulated chamber 68 within which the continuous coil is retained.

The cover and the bobbin which are each suitably molded from a resinous material (thermoplastic resins are presently preferred) provide for electrical insulation of the formed coil and also provide for mechanical protection against damage to the coil. The present assembly obviates the need for subsequent varnishing and baking of the formed electrical coil assembly as had been required previously.

It is seen that by the present invention, the inlet end or starting lead of the continuous wire is aflixed to one conductive terminal lug adjacent one end of the flange 30 and that the other or free end of the wire of the coil extends through a recess 36 in the flange 30 remote from the terminal lugs and then extends through a peripheral groove 38 in the flange 30 back toward the front for connection to the other conductive terminal 111g 32. By this arrangemnt, there is no crossover of the two leads and, therefore, possible shorting between the two leads of the continuous wire is obviated. Thus, it is evident that by the present invention there has been provided a unique electrical coil assembly having a molded cover and bobbin which provide an enclosed insulating chamber therebetween and which provide superior protection for the coil.

Another advantage of the bobbin and cover assembly of this invention is that it is provided with means for spacing and indexing the bottom of the cover and bobbin assembly on the support means therefor. Further, when the invention is employed in an alternating current relay, the shading piece of the alternating current relay is adapted to fit into a recess 44 in the top of the cover assembly. This construction assures positive positioning of the shading piece with respect to the electrical coil and also facilitates fastening of the relay onto the field piece of the alternating current relay.

Thus, it is seen that the cover and bobbin assembly for an electrical coil, made in accordance with this disclosure, provides superior mechanical protection from exterior damage to the formed coil and is less costly to manufacture than comparable coils wherein insulating tape and subsequent varnish, baking or impregnation cycles are utilized to form the completed product. By virtue of the construction of the cover and bobbin assembly from a molded insulated material, there is formed an enclosed, insulated chamber for protecting an electrical coil. The present design assures positive separation between the start and the finish leads and thus shorting between the leads of the coil is obviated.

The above disclosure has been given by way of illustration and elucidation and not by way of limitation, and it is desired to protect all embodiments of the herein disclosed inventive concept within the scope of the appended claims.

I claim:

1. An electrical coil assembly comprising in combination: a bobbin having first and second flanges, said second flange a peripheral edge, a tubular portion joining said flanges to define a space, a wound wire in said space, said wound wire having lead wires extending therefrom, a projecting shelf on said second flange, first and second terminal members projecting from said shelf, a pocket in said second flange passing from said first terminal member to said tubular portion, said pocket receiving and insulatingly spacing one lead wire from the remaining portions of said wound wire, a groove along a portion of said peripheral edge, said groove passing to said second terminal member and receiving the other lead wire, a removable cover member engaging said second flange and insulatingly covering said bobbin and said wound wire, a side portion on said cover member covering said groove and said other lead wire therein and forming an enclosed insulated passageway to thereby insulate said other lead wire from said one wire and said wound Wire.

2. An electrical coil assembly comprising in combination: a bobbin having first and second flanges, said second flange having a peripheral edge, a tubular portion joining said flanges to define a space, a wound wire in said space, said wound wire having lead wires extending therefrom, an outwardly projecting shelf on said second flange, first and second terminal members projecting u-p- Wardly from said shelf, a pocket in said second flange passing from a point adjacent said first terminal member to said tubular portion, said pocket receiving and insulatingly spacing one lead wire from the remaining portions of said wound wire, a groove along a portion of said peripheral edge, said groove passing to said second terminal member and receiving the other lead wire, slack provided in said lead wires so as to compensate for expansion and contraction of said wound wire in response to temperature variations, a cover member covering said bobbin and said wound wire and insulatingly enclosing said bobbin and said wound wire, said cover member including a downwardly extending side portion which covers said groove to define an enclosed insulated passageway to thereby insulate said other lead wire from said one lead wire and said wound wire, and cooperating means on said cover and on said flange for providing removable engagement therebetween.

3. An electrical coil assembly comprising in combination: a bobbin having first and second flanges, said second flanges having a peripheral edge, a tubular portion joining said flanges to define a space, a wound wire in said space, said wound wire having lead wires extending therefrom, an outwardly projecting shelf on said second flange, an outer end on said shelf, first and second terminal members projecting upwardly from said shelf, a projecting lip on said shelf positioned adjacent and below said terminal members, a pocket in said second flange passing from said first terminal member to said tubular portion, said pocket receiving and insulatingly spacing one lead wire from the remaining portions of said wound wire, a groove along a portion of said peripheral edge, said groove passing to said second terminal member and receiving the other lead wire, slack provided in said lead wires so as to compensate for expansion and contraction of said wound wire resulting from coil temperature variations, a removable cover member engaging said second flange and insulatingly covering said bobbin and said wound wire, apertures in said cover for permitting the passage of -said terminal members therethrou-gh, a downwardly extending side portion on said cover member, said downwardly extending side portion covering said groove and said other lead wire therein and forming an enclosed insulated passageway to thereby insulate said other lead from said one lead wire and said wound wire, a front portion on said cover spaced from the outer end of said shelf and adjacent said lip for defining a space between said outer end of said shelf and said front portion to provide said lead wires with suflicient space for electrically connecting to said terminal members.

References Cited by the Examiner UNITED STATES PATENTS 2,648,031 8/1953 Lang et a1. 336-136 X 2,735,967 2/1956 Lewus 317184 X 2,825,450 4/ 1958 Lambert 20652 2,922,932 1/1960 Glowacki 336192 X 2,941,172 6/1960 Sutton 336-198 X 3,131,371 4/1964 Brekke et a1. 336-192 JOHN F. BURNS, Primary Examiner. LARAMIE A. ASKIN, Examiner. 

1. AN ELECTRIC COIL ASSEMBLY COMPRISING IN COMBINATION: A BOBBIN HAVING FIRST AND SECOND FLANGES, SAID SECOND FLANGE A PERIPHERAL EDGE, A TUBULAR PORTION JOINING SAID FLANGES TO DEFINE A SPACE, A WOUND WIRE IN SAID SPACE, SAID WOUND WIRE HAVING LEAD WIRES EXTENDING THEREFROM, A PROJECTING SHELF ON SAID SECOND FLANGE, FIRST AND SECOND TERMINAL MEMBERS PROJECTING FROM SAID SHELF, A POCKET IN SAID SECOND FLANGE PASSING FROM SAID FIRST TERMINAL MEMBER TO SAID TUBULAR PORTION, SAID POCKET RECEIVING AND INSULATINGLY SPACING ONE LEAD WIRE FROM THE REMAINING PORTIONS OF SAID WOUND WIRE, A GROOVE ALONG A PORTION OF SAID PERIPHERAL EDGE, SAID GROOVE PASSING TO SAID SECOND TERMINAL MEMBER AND RECEIVING THE OTHER LEAD WIRE, A REMOVABLE COVER MEMBER ENGAGING SAID SECOND FLANGE AND INSULATINGLY COVERING SAID BOBBIN AND SAID WOUND WIRE, A SIDE PORTION ON SAID COVER MEMBER COVERING SAID GROOVE AND SAID OTHER LEAD WIRE THEREIN AND FORMING AN ENCLOSED INSULATED PASSAGEWAY TO THEREBY INSULATE SAID OTHER LEAD WIRE FROM SAID ONE WIRE AND SAID WOUND WIRE. 